Police say that around 1am today a Defence member was assaulted and a cache of weapons stolen from a Navy patrol boat moored at HMAS Coonawarra in Darwin.

In a statement, the Defence department said: "The intruder overpowered the duty member, accessed the vessel's armoury and removed a number of weapons. The person then departed the vessel with the weapons."

The number and types of weapons that have been stolen has not been divulged by authorities.

It is unclear whether the intruders accessed the boat from land or sea.